docs: def tempo(self,
                factor,
                use_tree=False,
                opt_flag=None,
                segment=82,
                search=14.68,
                overlap=12):
          """tempo takes 6 parameters: factor, use tree (True or False), option
          flag, segment, search and overlap).
  
          This effect changes the duration of the sound without modifying
          pitch.
          """
          self.command.append("tempo")
  
          if use_tree:
              self.command.append('-q')
          if opt_flag in ('l', 'm', 's'):
              self.command.append('-%s' % opt_flag)
          self.command.append(factor)
          self.command.append(segment)
          self.command.append(search)
          self.command.append(overlap)
          return self